The traction device includes a line mover. The line mover includes at least one movable friction surface. The friction surface in total defines at least two arc sections configured to move the line along with the arc sections. In use the line is wound around the friction surface such that the line includes a first contact area being in contact with the first arc section and a second contact area being in contact with the second arc section. Traction devices arc often used for paying out and retrieving a flexible line connected to a load, in general a heavy load. The flexible line may be a cable, rope, wire or the like.
The traction device may be used in any kind of hoisting system. In the situation that the traction device is located on a vessel, the traction device is often used for lowering or lifting heavy objects to or from the seabed. In this case one end of the line may be connected to the heavy object and the other end of the line may be connected to a winch for reeling in or out the line. The traction device is then coupled to the line between the winch and the heavy object. This means that the line runs from the winch, via the traction device to the heavy object. The traction device is coupled to the vessel and hears part of or substantially the full load during the lowering or lifting operation. Due to this the winch only bears the remaining part of the load during the lowering operation. This allows the lowering or lifting of very heavy objects to or from a seabed in a controllable manner.
U.S. Pat. No. 6,182,915 discloses a traction device including a line mover with multiple active rotation sheaves. Each active rotation sheave is drivable around a rotation axis and defines a friction surface with an arc section. Each active rotation sheave is provided with a separate driving unit to rotate the rotation sheave around the rotation axis thereof. This way the rotation speed of each rotation sheave can be optimized in relation to the velocity of the parts of the line being in contact with the different active rotation sheaves. This requires one or more very complex driving and control systems for controlling the rotation of the rotation sheaves. U.S. Pat. No. 6,182,915 also shows a further embodiment wherein the friction surfaces of the line mover arc formed by endless belts which are moveable along a track having the shape of a half circle.
An object of the traction device according the invention is to solve a problem of the prior art, or at least provide an alternative thereto.